In this work, LiClO4 was revisited and explored as a possible electrolyte in Li-ion batteries. LiClO4 and LiPF6 solutions in alkyl carbonate solvent mixtures were compared in several aspects: electrochemical windows with noble metal and aluminum electrodes, anodic stability, surface chemistry developed on negative electrodes (Li, Li-graphite, Li-Si), the electrochemical behavior of graphite anodes and LiMn 1/3Ni1/3Co1/3O2 cathodes, and thermal behavior (solutions alone and mixtures of solutions and electrode materials). The anodic stability and the aluminum passivation are much better in LiPF6 solutions than in LiClO4 solutions. However, HF contamination in the former solutions worsens the passivation of negative electrodes due to reactions with surface ROCO2Li and ROLi species. Thermal reactions of LiClO4 produce more specific heat than LiPF 6 solutions. However, in terms of onset temperatures for thermal runaway, the two electrolytes are equivalent. In conclusion, LiClO4 is still an electrolyte that may be considered for use in lithium-ion batteries.